Wheelchair drive apparatus

Abstract

A drive apparatus and method for continuously transmitting power to an axle to rotatingly drive the axle are disclosed. The drive apparatus includes a flexible ratch such as a flexible chain, belt, or cable, and cooperating first and second ratch engaging members for alternatively engaging the flexible ratch to continuously drive an axle. To operate the apparatus, one moves the first and second ratch engaging members in a first direction which causes the first ratch engaging member to engage and drive the flexible ratch which rotatingly drives the axle. One then reverses the ratch engaging members' direction of movement which causes the simultaneous releasing and engaging of the ratch by the first and second ratch engaging members, respectively, which continuously drives the axle.

What is claimed is: 
     
       1. An apparatus for use by a wheelchair occupant in manually propelling a wheelchair having a pair of propulsion wheels attached to the frame of the wheelchair comprising: a pair of first drive sprockets attached to and axially aligned with the propulsion wheels for driving the propulsion wheels;   a pair of axially aligned second and third drive sprockets attached to the frame of the wheelchair;   a pair of axially aligned fourth drive sprockets attached to the frame of the wheelchair;   a pair of first and second drive chains, said pair of first drive chains being slung about said pair of first and second drive sprockets, said pair of second drive chains being slung about said pair of third and fourth drive sprockets;   a pair of first handle means for gripping by a wheelchair occupant to enable the wheelchair occupant to make downward and upward strokes along a straight line; and   a pair of chain engaging means connected to said pair of first handle means for releasably engaging said pair of second drive chains to continuously drive said second drive chains in one direction during the wheelchair occupant's downward and upward strokes with said pair of first handles which, in turn, continuously drive said first drive chains, thereby propelling the wheelchair.   
     
     
       2. Apparatus as claimed in claim 1 wherein each chain engaging means includes: first chain engaging means for engaging said second drive chain during the wheelchair occupant's upstroke and for releasing said second drive chain during the wheelchair occupant's downward stroke; and   second chain engaging means for engaging said second drive chain during the wheelchair occupant's downward stroke and for releasing said second drive chain during the wheelchair occupant's upward stroke, said first and second chain engaging means cooperating so that one of said first and second chain engaging means engages said second drive chain as the other of said first and second chain engaging means releases said second drive chain.   
     
     
       3. An apparatus as claimed in claim 2 wherein each second drive chain has a plurality of connected chain links, each of which has opposing sides defining oppositely facing concave edges, and wherein each first and second chain engaging means includes simultaneous bearing means for simultaneously bearing against the oppositely facing concave edges of one chain link of said chain to engage and drive the chain. 
     
     
       4. An apparatus as claimed in claim 3 wherein both simultaneous bearing means of said first and second chain engaging means are mounted on a base and wherein each simultaneous bearing means includes a pair of first and second chain engaging members movably attached to said base for releasably engaging the oppositely facing concave edges of a chain link; and wherein said apparatus further comprises guide means for simultaneously directing said first and second chain engaging members into engagement with the oppositely facing concave edges of a chain link when said base is linearly moved along a line parallel to the direction in which said second drive chain is moved, said guide means also simultaneously directing said first and second chain engaging members out of engagement with the oppositely facing concave edges of a chain link when said base is linearly moved along said line in the opposite direction. 
     
     
       5. An apparatus as claimed in claim 4 wherein said guide means includes: an endless pulley-mounted main cable;   a disengaging pair of first and second cable segments, each of which is connected at a first end thereof to a location on said main cable, said first cable segment being connected at its other end to first said chain engaging member, said second cable segment being connected at its other end to said second chain engaging member, said disengaging pair of cable segments directing said first and second cable engaging members out of engagement with said second chain when the inertia of said main cable causes said first and second chain engaging members to move out of engagement with said second chain; and   an engaging pair of first and second cable segments, each of which is attached at one end thereof to a location on said main cable, said first engaging cable segment being connected at its other end to said first chain engaging member, said second engaging cable segment being connected at its other end to said second chain engaging member, said engaging cable segments directing said first and second chain engaging members into engagement with said second chain when the inertia of said main cable causes said first and second chain engaging members to move into engagement with said second chain.   
     
     
       6. An apparatus as claimed in claim 5 wherein said first handle means is attached to said base for driving said second drive chain in a forward direction. 
     
     
       7. An apparatus as claimed in claim 6 further comprising second handle means attached to said main cable for driving said second chain in a reverse direction wherein said disengaging pair of cable segments directs said first and second chain engaging members out of engagement with said second chain when the inertia of said base causes said first and second chain engaging members to move out of engagement with said second chain, and wherein said engaging pair of cable segments directs said first and second chain engaging members into engagement with said second chain when the inertia of said base causes said first and second chain engaging members to move into engagement with said second chain. 
     
     
       8. An apparatus as claimed in claim 5 wherein each of said engaging cable segments is of equal length so as to transmit inertial forces to and from said first and second chain engaging members simultaneously, and wherein each of said disengaging cable segments is of equal length so as to transmit inertial forces to and from said first and second chain engaging members simultaneously. 
     
     
       9. An apparatus as claimed in claim 1 further comprising track means extending between said third and fourth sprockets for slidably receiving said chain engaging means to maintain said chain engaging means in alignment with said second drive chain. 
     
     
       10. An apparatus as claimed in claim 9 wherein said track means includes ball bearing track sliding means slidably received in said track means for cooperating with said chain engaging means to maintain said chain engaging means in alignment with said second drive chain.